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plate&grid
Jun 25, 2024
In Show and Tell
Still a work a in progress, and a sharp eye will see quite a few mistakes and errors. Really impressed with this amp, opening my ears to music. At first it sounded great, but lacked bass. Swapped out the 0.22 uF caps for 0.33uF and it sounds much better. Currently running without shade feedback. Will be trying that soon. The bypass caps on the carhode resistor is also wrong. I must have not ordered those, so I swapped in 100uF caps I did not use in the power supply. Rather than use the third stage of filtering, I decided to use some 390uF caps for the second stage that I had extra for my power supply prototype test bed. Voltages are running the tubes at 96%. So need to watch it when installing the shade feedback. Future fixes Shade feedback Correcting the 12ax7 socket to something that looks better. Audio note cathode bypass capacitors on order 0.47 if coupling caps to try Possibly rebuilding with a larger power transformer. This does get hot. Selection switch needs to be improved. I used coax interconnect cable inside and it brings unloaded digital noise in when network streamer is not the selected source. Clean up wiring, install bottom cover and feet. Should keep me busy for a couple of months. Oh the layout…I think you had your tube sockets oriented differently. I decided to just push through and do a bit of an alternative layout. Wanted to get to the working state. Thanks again for making my first tube amp build a success…even if it is in process. I have followed along on the R8 modes, swan DIY 2.1A speakers, ear preamp, and now this litttle amp. Looking forward to the KT-88 amp build this summer, another load line refresher, and the output transformer impedance selection. It sounds so good. I hear stuff in the music I have never heard before. Imaging seems better too. Drives my Polk R700 speakers very well. Ear ringing 90 db range. Maybe a little less with feedback? Ps the neutral and line wires are swapped in this photo on the ice connector. Fixed during the initial power on tests.
My E34L amp build content media
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plate&grid
Dec 10, 2023
In Show and Tell
I am pleased with this build. If you have a 3d printer, you may want to give this build a try, or if you see one of these resonbly priced. This was about $150 to $200 build. Got the 6 liter ultrasonic cleaner on Black Friday sale. Could get a cheaper one as long as it is 6 Liters. Then bough 1 Rpm 12 volt ac motor, and Jamco electronics 12 volt ac wall wort and mating dc power receptacle, 6mm threaded rod, and 6mm to 7mm coupler from Amazon. I hear 40 kHz ultrasonic cleaners are best, probably could go cheaper with an unheated or non-digital unit as not sure if heating helps. Besides moving some of the pops and cracks, also improved bass response and mods and high detail noticeably for many of my used records. Word of caution though, it is loud and annoying when operating. I clean my records for 15 minutes on 25 deg c with one capful of record cleaner concentrate added to distilled water. The. Wipe and dry with clean microfiber, then give a final anti static brush wipe and records sound better. Not like new, but very noticble improvement over using just a brush, or brush and microfiber and cleaner. Below are some mother-in-law, unjacketed basement records. Got a whole box of dirty records with no sleeves or jackets. Many sound pretty good. Makes even the lightly used well kept records from record store sound better. Link to build files below at thingaverse. Not my design, but pleased with 3d print and the results. https://www.thingiverse.com/thing:4210025
Build to improve sound from records content media
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plate&grid
Nov 18, 2023
In Show and Tell
Update! Final version after painting. Holes were off for the tiubes, but I figured I could elongate the hole and use curtain rivets like Stephie suggested in one video to cover up my mistake and make it better looking at the same time. Also used auto body filler to clean up corners and fill the one accidental hole on the top. Hooked up one dc rail backwards and blew half my electrolytic capacitors. Luckily I bought 3 extra and had enough to replace. Also had bad hum on the channel that did not blow, but that was the input wire polarity swapped. Still have some hum at louder volume. Seems tp be 60hz and is real bad if phono preamp gnd is disconnected. Will try adding a bulkhead , once I get some aluminum sheet metal. Also will try some of the notes at the Lenco heaven page..try changing the caps to 33uF and bypass them. I did buy the lowest esr caps I could find at mouser. https://www.lencoheaven.net/forum/index.php?topic=20984.0(https://www.lencoheaven.net/forum/index.php?topic=20984.0) May end up putting it is a really big chassis and put it under my turntable, as I big, short copper strap between my turntable may kill the hum better. But it sounds good. I scrambled to get the first sounds out of this last night. I still have chassis issues to fix as not happy with placement of holes I punched thru the chassis for the tubes. So I have not bothered installing shielded wire for the audio path yet. I still need to cut a bigger hole around the tubes and add a trim plate with holes for the tubes aligned better, paint, and add the ground screw. Oh and add some shielding for the 60hz hum, but a lot of that goes away with the ground wire pressed to the chassis. I may just make a whole new chassis for it some point. Enjoyable build and your videos helped a lot. Would have never tried this or even thought of making one of these if it was not for your videos. Building this brought a lot of happiness into my life. Thank you! I am shocked, amazed, the bass is intense. My room is very hard to fill with bass, but this combined with the R8 is amazing. Some reviewers of my Polk R-700 speakers would complain that they can over pressurize the room. I had no idea what they were talking about till now. White Stripes, Ball and Biscuit sounds like the bass drum is in the room! So much better than my built in pre-amps and Fozi audio tube preamp that previously impressed me with better sound. I do need to figure out some ultrasonic filtering though.. I will post more photos as I clean it up and finsh the chassis and wiring. Capacitors. I am having a hard time sourcing capacitors. There is a pair of Mundorf evo oil on the other side, these purple clarity caps were available, so I bought them.
Phone stage build content media
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plate&grid
Oct 29, 2023
In Show and Tell
Got this kit on sale earlier in October on the prime day sales event. Spent more money on veneer than the kit. Curley Maple and black walnut burl. Sounds pretty good. Bright and dynamic speaker that gets the toes tapping. Bass is decent for the size. Glad I made this kit, learned a lot about veneering. I made a set of speakers years ago, but they did not sound good. I think I will revisit those speakers and see if I can fix them with mods to crossover. Thanks for leading the way on these projects, and sharing your knowledge and skills. Next project is the phone preamp. I have all the parts ready to go.
DIY2.2A kit build content media
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plate&grid
Sep 07, 2023
In Show and Tell
Getting to the end of my R8 mods. I made the changes is a bit of a different order. At some point I changed speakers and I started noticing a low frequency hum when the amp is turned up, or using the preamp input at any volume. After reading up on forums and the books you recommended, I realized I never moved the heater wire for the pre-amp. That got rid of a lot of the remaining noise and hum. Still has some hum though, but I have to practicaly put ear in woofer. For me the best sonic improvement was aplitting the voltage stabilizer tube into separate channels, as for some reason my left and righ channels were out of phase, but after completing this mode, the channels were in phase on the oscilloscope and made a noticeable sounds stage improvement. Not sure if I broke something along the way, and fixed it, or if amp was always like that. Next best improvement was adjusting the negative feedback. I left the 33k resisors in, but bypassed them with 120pf silver mica caps, which resulted in slightly rounded off 1k square wave and pretty good up till 10k, severe rounding at 20k square wave, but 20khz sine wave is barely reduced in amplitude. It sounds now so good. The brightness that was fatiguing to me on this amp and my speakers are gone.
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plate&grid
Aug 20, 2023
In Questions & Answers
I just learned that my speakers are 4 ohms for most of the lower frequencies, but I have been running in the 8 ohm output of my Willsenton R8 amp, as the speakers are labeled 8 ohm. The center power transformer ran very warm with the speakers plugged into the 8 ohm speaker outputs. Last night I tried using the 4 ohm outputs, the result was all 3 transformers were cool to the touch, slight warmth on center power, but nothing like before. I think I saw a video explaining that running lower impedance speakers than the output rating would overheat the output transformers. But in mine it was trying to overheat my power supply transformer. I guess the heat is coming from that for a given voltage amplification, it is putting out essentially twice the current. Thus the power transformer was getting hot. Is that right? Would there be negative effects of pulling too much current through the output tubes? Was the amp putting out over rated power? But not clipping because there was still voltage headroom to amplify more? Just trying to understand why solid state amps are built with bigger power supplies to handle lower impedance loads, but tube amplifiers are given different output transformer windings.
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plate&grid

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